Zener diode as a voltage regulator — practice questions

Question 1 · difficulty L1 · recall

A Zener diode used as a voltage regulator is normally operated in

• A. reverse breakdown
• B. forward bias below knee only
• C. zero bias
• D. open circuit with no current

Question 2 · difficulty L1 · understanding

The main purpose of a series resistor in a Zener regulator is to

• A. increase Zener voltage without limit
• B. limit current
• C. short the supply
• D. make the diode forward biased

Question 3 · difficulty L2 · understanding

In its regulation region, the voltage across an idealised Zener diode is approximately

• A. proportional to current like an ideal resistor
• B. zero
• C. constant at VZ
• D. equal to the supply regardless of series elements

Question 4 · difficulty L2 · application

A 6 V Zener is connected as a shunt regulator with adequate current. The regulated output is approximately

• A. 0.6 V
• B. 12 V
• C. zero
• D. 6 V

Question 5 · difficulty L3 · application

If input voltage rises moderately in a properly designed Zener regulator while load is fixed, the extra current mainly

• A. flows through the Zener
• B. forces output to rise by the same amount
• C. stops all current
• D. reverses the load current

Question 6 · difficulty L3 · application

If load current increases while input voltage remains fixed, Zener current generally

• A. increases by exactly the same amount
• B. decreases
• C. remains fixed regardless of load
• D. becomes forward current

Question 7 · difficulty L4 · analysis

A 12 V source feeds a 6 V Zener through 300 Ω with no load. Approximate Zener current is

• A. 2 mA
• B. 40 mA
• C. 20 mA
• D. 60 mA

Question 8 · difficulty L4 · analysis

Why can regulation fail if load current becomes too large?

• A. the Zener voltage becomes infinite
• B. the series resistor becomes a battery
• C. reverse bias automatically changes to AC
• D. Zener current may fall below the minimum needed to stay in breakdown

Question 9 · difficulty L5 · analysis

A Zener regulator has Vin=10 V, VZ=5 V and series resistor 250 Ω. Total available current is about

• A. 20 mA
• B. 2 mA
• C. 40 mA
• D. 50 mA

Question 10 · difficulty L5 · analysis

Why is a Zener diode preferable to an ordinary rectifier diode for simple reverse-voltage regulation?

• A. It never conducts in reverse
• B. It is designed for stable, specified reverse-breakdown operation
• C. It has no junction
• D. Its forward voltage is always exactly zero